JPH09157403A - Short carbon fiber aggregate, method for producing the same, and fiber reinforced resin composition - Google Patents

Abstract

(57) Abstract: A carbon fiber aggregate capable of mixing a large amount of carbon fibers with a resin and obtaining a resin composition exhibiting a high elastic modulus is provided. SOLUTION: This is a carbon short fiber aggregate formed by bundling short carbon fibers having a fiber length of 2 to 20 mm in a bulk density in the range of 450 to 650 g / l, and is a graphitized short carbon fiber aggregate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a short carbon fiber aggregate mainly used for producing a fiber reinforced resin composition by mixing with a resin, a method for producing the same, and a fiber reinforced resin composition using the same. More specifically, a fiber-reinforced resin composition that can be used in place of a metal die-cast material such as Al or the like and that has high rigidity, heat resistance, weight reduction, and moldability, and a carbon short fiber aggregate used therefor, It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, precision parts have been manufactured by a die-cast manufacturing method of a metal material from the viewpoint of elastic modulus, dimensional accuracy, heat resistance, etc. of the material. However, metal die-cast products require less processing than general shaving materials, but still require processing. Further, the die casting mold is expensive because it is used at a high temperature, and the additional equipment for melting the metal is also very expensive. There has also been a demand for weight reduction of precision machines.

Therefore, in recent years, a fiber-reinforced resin composition prepared by mixing and dispersing carbon fibers in various matrix resins has been evaluated for mechanical properties such as high strength, high rigidity, low specific gravity and high abrasion resistance, and is industrially used. Has been attracting attention as an important material. Particularly in the fields of precision parts and electronic application products, which have recently been reduced in size and weight, molded parts of highly rigid fiber-reinforced resin compositions have been used as metal substitute materials. However, replacement of conventional fiber-reinforced resin compositions has not progressed due to low rigidity, low heat resistance and the like. For example, as a material, even though it has a heat resistance of about 200 ° C., its thermal conductivity is low, so that there is a problem that it cannot be actually used because a high temperature portion is locally formed without the heat being released during use.

Conventionally, when such carbon short fibers are mixed and dispersed in various resins to obtain a fiber-reinforced resin material, a large number of carbon long fibers are bundled with a resin called a sizing agent and then cut into short pieces. A method of using the short carbon fiber bundle thus obtained and mixing it with a matrix resin is usually used.

On the other hand, when the present inventors have previously mixed the short carbon fiber bundles bundled with such a sizing agent with a resin composition for high temperature use, they are heated at high temperature and molded. In order to solve the problem that the generated gas hinders the work and causes voids in the molded body, carbon short fiber bundles bundled with a sizing agent are carbonized in the range of 400 to 1500 ° C in advance. It has been proposed (Japanese Patent Laid-Open No. 6-143483). It should be noted that the present invention does not disclose processing at higher temperatures.

On the other hand, in the field of fiber reinforced resin compositions, as small and lightweight molded parts are demanded, it is desired to mix carbon fiber as much as possible with resin to obtain a highly rigid fiber reinforced resin material. It is rare.

However, the conventional short carbon fiber bundle,
In the carbon short fiber aggregate in the carbonization step, various problems occur when trying to mix and disperse a large amount of carbon fibers, for example, 30 parts by weight or more of carbon fibers in 100 parts by weight of the resin. It was difficult to obtain a high content of carbon fibers, or it was difficult to obtain a carbon fiber reinforced resin material having high rigidity, that is, high elastic modulus due to insufficient dispersion. For example, if you try to supply a large amount of short carbon fiber bundles with a feeder, pills of short carbon fibers will be created, and clogging will occur in the supply process.
Alternatively, there has been a problem that the fibers cannot be uniformly dispersed in the matrix resin. Further, even if a short carbon fiber bundle is prepared by previously bundling carbon fibers having a high elastic modulus with a sizing agent, it is difficult to obtain a short carbon fiber aggregate having a high bulk density.

Further, in the field of particularly demanding compact and lightweight molded parts, it is required to obtain a fiber-reinforced resin composition having a high elastic modulus. In the conventional carbon fiber bundles and the like, carbon short fiber aggregates are used. Even if a large amount was mixed with the resin, the required high elastic modulus could not be obtained. Therefore, conventionally, an aggregate of carbon short fibers having a fiber length of 2 to 20 mm and a bulk density in the range of 450 to 650 g / l has not been known.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is easy handling, that is, good operability in the steps of mixing and dispersing, that is, carbon short that allows a large amount of carbon fibers to be mixed with resin. It is to obtain a short carbon fiber aggregate which is a fiber aggregate and in which a resin composition containing a large amount of carbon fibers exhibits a high elastic modulus, and a method for producing the same. Further, it has a high flexural modulus, is superior in flexural rigidity to a metal material having the same weight, is lighter in weight than a metal material having the same flexural rigidity, and is more than twice as good in thermal conductivity as a conventional resin composition. It is to provide a fiber-reinforced resin composition.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the maximum attainable temperature of carbon short fiber aggregates bundled with a sizing agent is 1600 ° C. or higher in an inert gas atmosphere. When heated and graphitized at a temperature of 3300 ° C. or less, a carbon short fiber aggregate composed of such short carbon fibers and a graphitized product of resin has good operability in the mixing and dispersing steps and Since it can be easily dispersed at the time of mixing, it becomes possible to mix a larger amount of carbon fibers in the resin than in the past, and at a level higher than that of a resin composition in which a large amount of such short carbon fiber aggregates was mixed. It was found that the compound also exhibits properties such as extremely high elastic modulus and thermal conductivity, and has reached the present invention.

That is, the gist of the present invention is that the fiber length is 2 to 20 m.
A carbon short fiber aggregate obtained by bundling carbon short fibers of m in a bulk density range of 450 to 650 g / l, wherein the carbon short fiber aggregate is graphitized, and is bundled with a sizing agent. A method for producing a carbon short fiber aggregate, comprising heating the carbon short fiber aggregate thus obtained in an inert gas atmosphere under conditions such that the highest temperature reaches 1600 ° C. or higher and 3300 ° C. or lower, and performing graphitization treatment, Carbon short fibers having a fiber length of 2 to 20 mm are aggregated in a bulk density range of 450 to 650 g / l, and graphitized carbon short fiber aggregates are blended in an amount of 30 parts by weight or more based on 100 parts by weight of the thermoplastic resin. The present invention resides in a fiber-reinforced thermoplastic resin composition.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The short carbon fiber in the present invention is a concept for a long fiber used in the production of prepreg and the like. As the carbon fiber used in the present invention, various conventionally known carbon fibers are used, and specifically, polyacrylonitrile-based, rayon-based, pitch-based, polyvinyl alcohol-based carbon fibers and the like can be mentioned, but especially mesophase. Pitch carbon fibers made from pitch are preferred.

Next, the method for producing the short carbon fiber aggregate of the present invention will be described. The carbon fiber is bundled with a sizing agent and then cut by a known cutting method to have a length of usually 2 to 20 mm, preferably 3 to.
It is cut to 12 mm and used in the next graphitization process. As the sizing agent, any of those commonly used for this purpose can be used, and among them, those having good monofilament convergence may be selected. Specifically, epoxy compounds, polyurethane compounds, saturated or unsaturated polyester, polyphenylene sulfite, polyphenylene ether, polycarbonate, polyoxymethylene, polystyrene, polyolefin, acrylic resin, vinyl acetate resin, ethylene vinyl acetate copolymer, polyamide resin and the like Homopolymers or copolymers are exemplified. this house,
An epoxy compound or a water-soluble polyamide compound is particularly preferable.

The amount of the sizing agent to be used is not particularly limited as long as it can exert the effect of assembling without excess or deficiency, and there is no particular difference from the amount of the sizing agent to be applied during normal sizing. Specifically, it is 0.1 with respect to the total amount of short carbon fibers.
10 to 10% by weight, more preferably 0.5 to 7% by weight. If the amount of the sizing agent attached is less than 0.1% by weight, the short carbon fiber aggregate will have a poor sizing property, and if it exceeds 10% by weight, the short carbon fiber aggregate will have too good a sizing property and will be dispersed in the resin. Is deteriorated and the physical properties of the short carbon fiber reinforced thermoplastic resin are deteriorated, which is not preferable.

A specific method for bundling the short carbon fibers with a sizing agent may be a known method, for example, a bundle of hundreds to hundreds of thousands of long carbon fibers may be impregnated with the sizing agent and then dried. As the impregnation method at this time, a method of dissolving the sizing agent in a solvent and using it as a solution, dispersing in a solvent to use as an emulsion, and using it by heating and dissolving can be considered. Because the viscosity of the resin is high, it is difficult to remove the sizing agent once attached to the carbon fiber.It is difficult to adjust the amount of the sizing agent. It is not preferable because physical properties such as heat resistance of the whole composition may be adversely affected.

Solvents used for dissolving or dispersing the sizing agent include 2-butanone, tetrahydrofuran, N, N-dimethylformamide, acetone, chloroform, dichloromethane alcohol, water and the like. In the solution or emulsion containing the sizing agent, a surfactant, a silane coupling agent, an epoxy curing agent, a catalyst, an adhesive, and the like may be added as necessary.

The surfactant used in the emulsion is, for example, castor oil ether of polyoxymethylene,
At least one surface active agent selected from polyoxyethylene alkyl ethers such as nonyl phenyl ether and styrenated phenyl ether or polyoxyethylene alkyl allyl ether, and polyvinyl alcohol.

Next, the conditions for graphitizing treatment after the sizing agent is used for focusing will be described. Graphitization is carried out in an inert gas, in vacuum or in a graphite breeze so that the short carbon fibers do not come into contact with air, and the maximum attainable temperature is 1600 ° C or higher and 3300 ° C or lower, preferably 1800 ° C or higher and 3300 ° C or lower, and more preferably 2000 ° C. The above is performed at a temperature of 3300 ° C. or lower.

The rate of temperature increase up to the maximum temperature is not particularly limited, but is usually in the range of 0.1 ° C./hour to 200 ° C./hour. It is also possible to carry out the carbonization treatment once at a temperature of 400 ° C. or more and 1500 ° C. or less and then move it to the same heat treatment equipment or another graphitization treatment equipment for graphitization treatment. The oxygen concentration during graphitization is preferably 500 ppm or less. The presence of more oxygen than this is not preferable because the carbon short fibers will undergo oxidative deterioration.

The above graphitization treatment is carried out by adjusting conditions such as temperature and time so that graphite crystals are formed to some extent in the resulting short carbon fiber aggregate. The formation of graphite crystals can usually be determined by a powder X-ray diffraction method d
002 is 3.45 Å or less and 3.36 or more, preferably 3.
It can be known by being 43 or less and 3.36 or more. As long as the d002 of the graphite crystal can be examined, it can be examined not only by the powder X-ray diffraction method but also by a high-resolution transmission electron microscope or electron beam diffraction method.

Further, in order to measure the tensile elastic modulus of the carbon short fiber thus obtained, when a carbon long fiber is manufactured under the same conditions except that there is no cutting step and a tensile elastic modulus test is conducted, It is preferable to use short carbon fibers having an elastic modulus of 50 T / mm ² or more. The short carbon fiber aggregate of the present invention thus obtained has a bulk density of 450 g / l or more and 650 or more.
g / l or less, preferably 550 g / l or more and 650
It is g / l or less.

Further, the short carbon fiber aggregate of the present invention has a weight loss of 0.5% or less when heated at 400 ° C. and 1 atm in an inert gas atmosphere for 0.5% or less, and is hardly decomposed by heating during molding. Therefore, the generation of gas is very small. Furthermore, the short carbon fiber aggregate of the present invention has a low content of impurity ash and is 100 ppm or less, preferably 50 ppm or less. The ash content is measured as the weight of the non-combustible ash component remaining after the carbon element is burned in air at a temperature of 800 ° C. or higher for a sufficient time, for example, 300 minutes or longer.

Next, a fiber-reinforced resin composition using such a short carbon fiber aggregate as a reinforcing material will be described. The resin used is a known resin, preferably a thermoplastic resin, for example, polycarbonate, polystyrene, polyester, polyolefin, acrylic resin, polyoxymethylene, polyphenylene ether, polyphenylene oxide, polybutylene terephthalate, polyether ether ketone, polyphenylene sulfone. , Polymers such as fluororesins, or copolymers thereof, and the like. Particularly, the short carbon fiber aggregate of the present invention has a heat resistance which has been a particular problem in the past due to its high molding temperature. The effect is great when applied to the production of a fiber-reinforced resin composition using super engineering plastic as a matrix resin. The heat resistant super engineering plastic is not particularly limited including conventionally known ones, but preferably polyether ether ketone, polyether ketone, polyether ketone ketone, polyether sulfone, polyphenylene sulfide, polyarylene sulfide, polyether. It is preferable to use imide, polyimide, polyarylate, polysulfone, polyamideimide, liquid crystal polymer and the like and their blends.

Also, crystalline resins such as polyamide, A
S resin, polyphenylene sulfide, LCP, a mixture thereof and the like are preferable because the moldability is secured even when the carbon fiber is highly filled.

The resin composition of the present invention is a mixture of these components.
30 to 280 parts by weight of short carbon fiber aggregates, preferably 35 to 250 parts by weight, more preferably 4
The amount is preferably 0 to 200 parts by weight. If the carbon short fiber aggregate is less than 30 parts by weight with respect to 100 parts by weight of the resin, the reinforcing effect of the carbon fibers is not exhibited, while if it is 280 parts by weight or more with respect to 100 parts by weight of the thermoplastic resin, it is mixed with the matrix resin. However, various problems are likely to occur in the dispersion process.

The resin composition of the present invention can preferably achieve a flexural modulus of 150,000 kg / cm ² or more. Further, it is preferable that the volume resistivity is 100 Ωcm or less and the thermal conductivity in the direction perpendicular to the oriented fiber is 0.7 W / mK or more and the thermal conductivity in the direction parallel to the oriented fiber is 4 W / mK or more.

The compounding method of such a resin and the short carbon fiber aggregate of the present invention is not particularly limited, but is usually a single-screw extruder, a twin-screw extruder, a press machine, a high speed mixer, an injection molding machine. , A pultrusion molding machine or the like.
Further, to the extent that the effects of the present invention other than the above components are not impaired, other types of carbon fibers, glass fibers, aramid fibers, boron fibers, silicon carbide fibers, short fibers and long fibers such as fibers of the above resins, whiskers, Metal coating fibrous reinforcing agents such as nickel, aluminum and copper,
Alternatively, a reinforcing agent composed of fillers such as carbon black, molybdenum disulfide, mica, talc, and calcium carbonate, a stabilizer, a lubricant, and other additives can be added.

[0028]

INDUSTRIAL APPLICABILITY The short carbon fiber aggregate of the present invention can mix a large amount of carbon fibers with a resin and can obtain a resin composition having a high elastic modulus. In addition, it maintains the state of the aggregate itself, is easy to handle, has good workability such as being easily dispersed when mixed with a resin, and generates very little gas even when heated at high temperature during molding, Gives a compact with few voids.

According to the method for producing a short carbon fiber aggregate of the present invention, such a useful short carbon fiber aggregate can be produced easily and industrially advantageously. The fiber-reinforced resin composition of the present invention has very few voids and is excellent in mechanical properties. Furthermore, since it has a high carbon fiber content and a high elastic modulus (high rigidity), it has superior rigidity compared to an aluminum alloy of the same weight,
It can also be made lighter than an aluminum alloy of the same rigidity. or,
Since the thermal conductivity is high, a local high temperature portion is unlikely to occur, and a fiber-reinforced resin composition having practical heat resistance can be obtained.

[0030]

【Example】

(Example 1) Production of short carbon fiber aggregates Pitch-based carbon fibers having a tensile strength of 240 kg / mm
² , tensile elastic modulus 22 ton / mm ² , fiber diameter 10μ,
Epoxy compound “Epicoat 834” (manufactured by Shell Chemical Co., Ltd.) 60 parts by weight and “Epicoat 1004” (manufactured by Shell Chemical Co., Ltd.) having a density of 2.01 g / cm ³ and a filament number of 8000 were used in an emulsion concentration of 3% by weight. After being impregnated with a water emulsion solution prepared so as to have the following composition, it is heated and dried at about 120 ° C. for 20 minutes, and further cut with a cutting machine to a carbon short fiber aggregate having a length of 6 mm (epoxy compound adhesion amount is 3.1% by weight). Was manufactured. Then in argon gas 2
The temperature was raised to 000 ° C., the temperature was maintained for 1 hour, then the temperature was cooled to obtain a graphitized short carbon fiber aggregate. The obtained short carbon fiber aggregates had a bulk density of 610 g / l and was 88 in air.
Measured ash content after burning for 40 hours at 0 ° C is 67ppm
Met.

Further, powder X-ray diffraction was measured using silicon as a standard sample (in accordance with the method for measuring the lattice constant and the crystallite size of artificial graphite defined by the Committee for Carbon Materials 117 of Japan Society for the Promotion of Technology). The surface spacing d002 is 3.42
Was Å. On the other hand, in order to measure the tensile elastic modulus of the carbon fibers constituting the short carbon fiber aggregate (measurement of the tensile elastic modulus is difficult with short fibers), the same as above except that the cutting step is not performed. The tensile elastic modulus of the carbon long fiber produced by the method was measured and found to be 60 ton /
It was mm ² .

Production of Reinforcing Fiber Resin Composition 43 parts by weight of the short carbon fiber aggregate and 100 parts by weight of dried polybutylene terephthalate resin pellets (“Novadur 5008” manufactured by Mitsubishi Engineering Plastics Co., Ltd.) were dry blended and then screw extruded. Machine, melt mix at 250 ° C, extrude into strands,
After cooling with water, it was cut into pellets. The charging into the extruder was smooth, gas was hardly generated during pelletization, and the short carbon fiber aggregate and the resin were in a uniformly dispersed state. The carbon short fiber reinforced molding material thus obtained is dried at 120 ° C. for 6 hours and then molded by injection molding,
A test piece (A) was obtained.

Further, those in which the mixing ratio of the short carbon fiber aggregates to the resin pellets was changed to 25 parts by weight (Test piece B) and 11 parts by weight (Test piece C) were prepared. The moldability and flexural modulus of the obtained test piece are shown in Table-1 and Figure-1. The flexural modulus of the test piece is ASTM
It was measured according to the D790 method (hereinafter, all bending elastic moduli were measured according to this method).

Comparative Example 1 Production of Short Carbon Fiber Assembly A short carbon fiber assembly was produced in the same manner as in Example 1 except that the carbon fibers bundled with the sizing agent were not fired. The obtained short carbon fiber aggregate has a bulk density of 580 g / l.
The ash content measured after burning for 40 hours at 880 ° C. in air was 200 ppm.

Powder X-ray diffraction was measured using silicon as a standard sample (in accordance with the method for measuring the lattice constant and crystallite size of artificial graphite defined by the Japan Society for the Promotion of Technology 117 Committee for Carbon Materials). The surface spacing d002 is 3.47.
Was Å.

Manufacture of Reinforced Fiber Resin Composition A test piece of a carbon short fiber reinforced molding material in which the mixing amount was changed was obtained in the same manner as in Example 1 except that the above short carbon fiber aggregate was used. That is, a test piece containing 43 parts by weight of the short carbon fiber aggregate (a), a test piece containing 25 parts by weight (b), 11
Let the test piece of a weight part be (c).

The moldability and flexural modulus of the obtained test piece are shown in Table 1 and FIG.

(Example 2) Using the short carbon fiber aggregate obtained in Example 1, 43 parts by weight of the short carbon fiber aggregate and dried polyetherimide resin pellets ("Ultem 1010" manufactured by GE Plastics Co., Ltd.) ) After dry blending with 100 parts by weight, the mixture is put into a screw extruder,
The mixture was melt-mixed at 390 ° C., extruded into a strand, cooled with water, and cut into pellets. The extruder was smoothly charged, and the carbon short fiber aggregate and the resin were in a uniformly dispersed state with almost no gas generation during pelletization. The carbon short fiber reinforced molding material thus obtained was treated at 120 ° C.
After drying for 6 hours, injection molding was performed to obtain a test piece (D).

Further, the mixing ratio of the short carbon fiber aggregates to the resin pellets was changed to 17 parts by weight (test piece E).
It was created. The moldability and flexural modulus of the obtained test piece are shown in Table-1 and Figure-1.

Comparative Example 2 Production of Short Carbon Fiber Aggregate The carbon fibers used in Example 1 were bundled with the same sizing agent as in Example 1 and then cut into 6 mm lengths. This product was carbonized at a maximum temperature of 400 ° C. to obtain a short carbon fiber aggregate.

That is, the pitch-based carbon fiber has a tensile strength of 240 kg / mm ² and a tensile elastic modulus of 22 ton / m.
Epoxy compound "Epicoat 834" (manufactured by Shell Chemical Co., Ltd.) 60 parts by weight and "Epicoat 1004" (manufactured by Shell Chemical Co., Ltd.) 40 parts by weight with m ² , fiber diameter 10μ, density 2.01 g / cm ³ , and filament number 8000. Was impregnated with a water emulsion solution prepared to have an emulsion concentration of 3% by weight, then dried by heating at about 120 ° C. for 20 minutes, and further cut by a cutting machine with a carbon short fiber aggregate of 6 mm length (epoxy compound adhesion amount Produced 3.1% by weight).
After that, the temperature was raised to 400 ° C. in argon gas, and the temperature was maintained for 1 hour, followed by cooling to obtain a carbon short fiber aggregate. The obtained short carbon fiber aggregate has a bulk density of 590 g / l.
The ash content measured after burning for 40 hours at 880 ° C. in air was 200 ppm.

Powder X-ray diffraction was measured using silicon as a standard sample (in accordance with the method for measuring the lattice constant and the crystallite size of artificial graphite defined by the Japan Society for the Promotion of Technology 117 Committee for Carbon Materials). The surface spacing d002 is 3.47.
Was Å.

Production of Reinforcing Fiber Resin Composition Test pieces of short carbon fiber reinforced molding material with different mixing amounts were obtained in the same manner as in Example 2 except that the obtained short carbon fiber aggregate was used. That is, a test piece containing 43 parts by weight of the short carbon fiber aggregate was designated as (d) and a test piece containing 17 parts by weight was designated as (e). The moldability and flexural modulus of the obtained test piece are shown in Table-1 and Figure-1.

Comparative Example 3 Production of Short Carbon Fiber Aggregate The carbon fibers used in Example 1 were bundled with the same sizing agent as in Example 1, and then cut into 6 mm lengths. This product was carbonized at a maximum reaching temperature of 1000 ° C. to obtain a short carbon fiber aggregate.

That is, the pitch-based carbon fiber has a tensile strength of 240 kg / mm ² and a tensile elastic modulus of 22 ton / m.
Epoxy compound "Epicoat 834" (manufactured by Shell Chemical Co., Ltd.) 60 parts by weight and "Epicoat 1004" (manufactured by Shell Chemical Co., Ltd.) 40 parts by weight with m ² , fiber diameter 10μ, density 2.01 g / cm ³ , and filament number 8000. Was impregnated with a water emulsion solution prepared to have an emulsion concentration of 3% by weight, then dried by heating at about 120 ° C. for 20 minutes, and further cut by a cutting machine with a carbon short fiber aggregate of 6 mm length (epoxy compound adhesion amount Produced 3.1% by weight).
After that, the temperature was raised to 1000 ° C. in argon gas, and the temperature was maintained for 1 hour, followed by cooling to obtain a carbon short fiber aggregate. The obtained short carbon fiber aggregate has a bulk density of 590 g / l.
And the ash content measured by burning in air at 880 ° C. for 40 hours was 180 ppm.

Further, powder X-ray diffraction was measured using silicon as a standard sample (in accordance with the method for measuring the lattice constant and crystallite size of artificial graphite defined by the Committee for Carbon Materials 117 of the Japan Society for the Promotion of Technology). The surface spacing d002 is 3.47.
Was Å.

Manufacture of Reinforced Fiber Resin Composition A test piece of a carbon short fiber reinforced molding material in which the mixing amount was changed was obtained in the same manner as in Example 2 except that the obtained short carbon fiber aggregate was used. That is, a test piece containing 43 parts by weight of the short carbon fiber aggregate was designated as (d '), and a test piece containing 17 parts by weight was designated as (e'). The moldability and flexural modulus of the obtained test piece are shown in Table-1 and Figure-1.

[0048]

[Table 1]

(Example 3) The short carbon fiber aggregate produced in Example 1 was used as the short carbon fiber aggregate, PPS resin manufactured by Mitsubishi Engineering Plastics Co., Ltd. was used as the matrix resin, and the amount of carbon fiber was compound (resin). The composition was weighed so as to be 45% by weight (the amount of the short carbon fiber aggregate was 82 parts by weight with respect to 100 parts by weight of the matrix resin) and dry blended. The material was charged from the hopper of a twin-screw extruder, and the kneaded and extruded strand was cooled while being drawn and cut with a strand cutter to obtain a pelletized compound. A test piece was molded by an extrusion molding machine.

Example 4 A test piece was prepared in the same manner as in Example 3 such that the amount of short carbon fiber aggregates was 60% (the amount of short carbon fiber aggregates was 150 parts by weight relative to 100 parts by weight of matrix resin). Was molded. (Example 5) The same carbon fiber as in Example 3 was supplied from the side feed of the twin-screw extruder and the PPS resin was supplied from the top feed of the twin-screw extruder to carry out kneading and extrusion. A test piece was molded in the same manner below.

Example 6 A test piece was prepared in the same manner as in Example 3 such that the amount of short carbon fiber aggregates was 30% (the amount of short carbon fiber aggregates was 43 parts by weight relative to 100 parts by weight of matrix resin). Molded.

Comparative Example 4 A test piece was prepared in the same manner as in Example 3 such that the amount of short carbon fiber aggregates was 15% (18 parts by weight of short carbon fiber aggregates per 100 parts by weight of matrix resin). Molded. (Comparative Example 5) Kneading was carried out in the same manner as in Example 3 such that the amount of the short carbon fiber aggregates was 75% (the amount of the short carbon fiber aggregates was 300 parts by weight with respect to 100 parts by weight of the matrix resin). But I couldn't get the compound.

(Comparative Example 6) Carbon fiber (elastic modulus 22 T / mm) which was used in Comparative Example 1 but was not baked after applying the sizing agent.
Kneading was carried out in the same manner as in Example 3 except that ² ) was used so that the amount of carbon fiber was 60%, but a large amount of gas was generated and a uniform compound could not be obtained. (Comparative Example 7) A carbon fiber amount was set to 60% by the same method as in Example 3 except that the carbon fiber having a firing temperature of 400 ° C. (elastic modulus 22 T / mm ² ) used in Comparative Example 2 was used. After kneading, a uniform compound could not be obtained.

[0054]

[Table 2]

The carbon fiber elastic modulus is a value measured by a method using JIS R7601 single filament, and the volume resistivity value is SRIS2301 "the Socie".
tyof Rubber Fndustry Stan
It was measured by the method of "dard in Japan".
The thermal conductivity in the A direction means that the central part of the ASTM tensile test piece is cut out and measured in the thickness direction of the tensile test piece, that is, in the direction perpendicular to the fibers oriented in the test piece,
The thermal conductivity in the B direction means the central part 4 of the ASTM tensile test piece.
Using a piece cut out by bonding with an adhesive, it means the one measured in the longitudinal direction of the tensile test piece, that is, in the direction parallel to the fibers oriented in the test piece. The flash method was measured in accordance with JIS R1611.

Using the results shown in Table 2 above as a comparison of the bending rigidity of plates having the same weight, a typical aluminum alloy (2014:
The bending elastic modulus of 7.4 T / mm ² and the specific gravity of 2.8 g / cm ³ ) are also shown in Table-3. When the weights are the same, the material of this example has a small specific gravity and thus can have a large plate thickness. The bending rigidity of a plate is the product of the elastic modulus of the material and the second moment of area, and the second moment of area is proportional to the cube of the plate thickness. Therefore, the necessary plate thickness and the necessary weight ratio for exhibiting the same bending rigidity are shown in Table-4, but in the case of the embodiment of the present invention, the necessary weight is less than that of the aluminum alloy, It is possible to provide a material that is light in weight and has a thermal conductivity that is at least twice as good as that of a conventional resin composition.

[0057]

[Table 3]

[0058]

[Table 4]

[Brief description of the drawings]

FIG. 1 is a diagram showing bending elastic moduli of test benches of Examples 1 and 2 and Comparative Examples 1, 2, and 3.

[Explanation of symbols]

 1 Example 1 2 Example 2 3 Comparative Example 1 4 Comparative Example 2 5 Comparative Example 3

Claims (7)

[Claims] 1. A carbon short fiber aggregate obtained by bundling short carbon fibers having a fiber length of 2 to 20 mm in a bulk density in the range of 450 to 650 g / l, which is graphitized. Carbon short fiber aggregate. 2. The short carbon fiber aggregate according to claim 1, wherein the content of the impurity ash is 100 ppm or less. 3. A d002 value of the carbon short fiber aggregate measured by a powder X-ray diffraction method is 3.45Å or less and 3.36Å or less.
It is above, The carbon short fiber aggregate of Claim 1 or 2 characterized by the above-mentioned. 4. The maximum attainable temperature of the short carbon fiber aggregates bundled with a sizing agent is 1600 ° C. in an inert gas atmosphere.
A method for producing a short carbon fiber aggregate, which comprises heating and performing graphitization under the condition of 3300 ° C. or lower. 5. A carbon short fiber aggregate formed by graphitizing carbon short fibers having a fiber length of 2 to 20 mm and having a bulk density of 450 to 650 g / l to 100 parts by weight of a thermoplastic resin. A fiber-reinforced resin composition comprising 30 parts by weight or more. 6. The short carbon fibers have a tensile elastic modulus of 50 T / mm.
The fiber-reinforced resin composition according to claim 5, which is ^two or more mesophase pitch carbon fibers. 7. The flexural modulus of the resin composition is 15,000.
0 kg / cm ² or more, a volume resistivity of 100Ωcm or less, the fiber-reinforced resin composition according to claim 5, wherein the thermal conductivity of 0.7 W / mK or more.